1. Field of Invention
The present invention relates to a computer case, and more particularly, to a computer case retention structure for fixing a cover to a base.
2. Related Art
The case of the conventional horizontal-type computer is formed by a cover and a base. The cover has a top plate and two side plates, wherein the two side plates are perpendicular to bottom plate and extended from two opposing edges thereof. The base has a bottom plate, a front plate, and a back plate. When the cover is placed on the base, the two side plates, the front plate, and the back plate form a containing space between the top and bottom plates. Electronic devices of the computer, for example, motherboard, central processing unit, hard disc drive, and optical disc drive, are placed on the base, thus the electronic devices are protected after the cover is fixed onto the base.
As for the conventional approach of fixing the cover to the base, several screw holes are formed on the back plate, and a lug or extension wing with a through hole is extended from the edge of the side plate. After the cover has been placed on the base, the lug (or extension wing) leans on the back plate, and the through hole of the lug overlaps the screw hole. Then a screw is passed through the through hole to be screwed into the screw hole. Therefore, the cover is fixed onto the base by the screw.
In the approach of fixing the cover onto the base by screws, assembling tools are required for screwing or unscrewing the screws when the cover is going to be fixed onto the base or to be removed from the base, and thus it is inconvenient for maintenance and assembling of the electronic devices. Although some manufacturers enable the screws to be screwed by hands, it is still inconvenient that many screws are required to be screwed or unscrewed when the cover is going to be fixed onto the base or to be removed from the base. Therefore, there are improved computer case retention structures that are able to be operated by hands, wherein the cover can be released by pressing the computer case retention structures, such as those disclosed in the U.S. patents of U.S. Pat. Nos. 5,743,606, 5,918,956, 5,995,363, 6,074,028, and 6,367,896. In each of those mentioned above, the cover is fixed onto the base by engaging an elastic hook with a slot.
Referring to FIGS. 1A and 1B, it is a partial cross-sectional view of a cover 1 and a base 2 in the prior art, wherein an elastic hook 3 with latching portion 3a formed at the tip thereof is disposed on the inner side of the cover 1. The cover 1 has an opening 1a, and a lump 3b fixed on the elastic hook 3 is located in the opening 1a. A fixing element 4 with a slot 4a is disposed on the inner side of the base 2. When the cover 1 is placed on the base 2, the latching portion 3a is engaged with the slot 4a to fix the cover 1 onto the base 2, and thus the cover 1 cannot be moved relative to the base 2, as shown in FIG. 1A. When removing the cover 1 from the base 2, a force is applied through the opening 1a from the outside of the cover 1 to push the lump 3b inward, so as to push the elastic hook 3 for releasing the latching portion 3a from the slot 4a. Then the elastic hook 3 is disengaged from the fixing element 4, as shown in FIG. 1B. And therefore the cover 1 can be removed from the base 2. However, permanent deformation of the elastic hook 3 occurs with frequently repeated pressing or over-pressing acted. Thus the elastic hook 3 cannot be completely engaged with the slot 4a, and the fixing of the cover 1 is negatively affected. Since the lump 3b is located in the opening 1a formed on the cover 1, the exposed part of the lump 3b through the opening 1a is depressed inward if the permanent deformation of the elastic hook 3 occurs. And the overall appearance of the computer case and the fixing of the cover are both negatively affected. Therefore, it has become an essential issue to prolong the lifetime of the elastic hook, preventing the fatigue of material or permanent deformation occurring.